The present invention relates to a liquid crystal display device, and more particularly, to the art efficiently applied to an in-cell type liquid crystal display device with a built-in touch panel.
The display device is provided with a unit for inputting information (hereinafter referred to as a touch sensor or a touch panel) through touch operations (contact-pressing operation which will be simply referred to as touching) on the display surface by means of a user's finger or a pen, and used for mobile electronic devices, for example, PDAs and mobile terminals, various kinds of home electric appliances, and automated teller machines.
As the aforementioned touch panel, an electrostatic capacity system for detecting change in the capacity of the touched area has been known.
For example, as JP-A-2009-258182 discloses, the in-cell type liquid crystal display device with a touch panel function built-in the liquid crystal display panel has been well known as the electrostatic capacity type touch panel.
A scanning electrode for the touch panel of the in-cell type liquid crystal display device is derived from dividing a counter electrode (common electrode) formed on a first substrate (TFT substrate) into blocks, which constitutes the liquid crystal display panel.
The touch panel of the in-cell type liquid crystal display device is of coupling capacity detection type, and detects a touched position through detection of a cross capacity Cxy between the scanning electrode formed on the first substrate of the liquid crystal display panel and a detection electrode formed on a second substrate of the liquid crystal display panel.
The cross capacity Cxy has to be calibrated because of individual difference and variation in the plane resulting from variation and non-uniformity in permittivity and thickness of the liquid crystal layers, glass substrates that constitute the first and the second substrates, polarizing plates and adhesive resins.
In the shipment inspection stage of the touch panel of the in-cell type liquid crystal display device, the metal plate with the area sufficient to cover the entire surface of the touch panel is disposed. If the difference values of all the intersections of the scanning electrodes and the detection electrodes in Raw data between the cases before and after disposing the metal plate are within the specified range, the touch panel may be considered as being acceptable.
The metal plate inspection may be carried out within a short period of time. Meanwhile, it is difficult to detect the adjacent short-circuit failure between the two adjacent detection electrodes. The aforementioned adjacent short-circuit failure includes the one which occurs in the wiring on a flexible wiring substrate connected to the two adjacent detection electrodes.
The adjacent short-circuit failure between the two adjacent detection electrodes may be detected through the point inspection for each intersection between the scanning electrodes and the detection electrodes. However, it takes time for the inspection, thus significantly deteriorating the production efficiency. The method of conducting an open short-circuit inspection with a test pad disposed on the wiring connected to the detection electrode on the flexible wiring substrate has a disadvantage of higher susceptibility to noise and static electricity, or increase in size of the flexible wiring substrate.